Copper surged to the highest level in more than two years, lifting shares of producers including Glencore Plc, on expectations that demand in China will fuel a global shortage, with plans in the country to curb metal-rich waste imports reinforcing a bullish outlook.

Benchmark three-month prices rallied as much as 2.8 percent to $6,400 a metric ton, the highest since May 2015, and were at $6,296 at 11:09 a.m. in London. That’s a fourth day of gains, and adds to Tuesday’s 3.3 percent jump.

“We’re getting into rarefied air here, and we’ll probably need an oxygen mask to move higher,” said Robin Bhar, an analyst at Societe Generale AG.

Base metals have rallied in the past month as economists have become more upbeat about the trajectory of China’s economy, while concerns over tightening liquidity in the world’s top user have eased. Initial data for July have added to a positive picture. The world’s top metal user is also said to be planning a ban next year on some imports of machinery waste and other products for the purpose of extracting metals scrap, which may reduce supply.

“The market is very heated,” Xu Maili, an analyst at Everbright Futures Ltd., said from Shanghai. “There is an outbreak of bullish sentiment following recent good macro data.”

The ban, if enforced, may cut scrap imports by as much as 900,000 tons a year of contained copper, SMM Information & Technology Co. said in a note on its website, adding that some of the projected impact may be offset by increased local supply. Last year, scrap imports were about 3.3 million tons, customs data show. Nationwide refined-copper consumption was 11.6 million tons in 2017, according to the World Bureau of Metal Statistics.

Cutting Pollution

The potential waste move, aimed at cutting pollution, will probably reduce imports of low-grade copper scrap, according to He Xiaohui, an analyst at state-backed researcher Antaike Information Development Co. Still, the eventual impact may be limited as smelters buy higher-grade scrap instead, or improve the grades overseas before importing, He said by phone from Beijing.

The global copper market had a 65,000 ton deficit in the first five months of this year, according to the World Bureau of Metal Statistics. There’s a similar picture from the International Copper Study Group, which estimated the shortfall at 53,000 tons in April, paring the year’s surplus to just 80,000 tons.

Freeport-McMoRan Inc., the world’s biggest publicly traded producer, reckons further gains are likely. Chief Executive Officer Richard Adkerson said a looming deficit will benefit the company, with prices expected to hit $4 a pound ($8,818 a ton) or higher, according to remarks on a conference call.

Aluminum also rallied on the LME amid speculation that China’s efforts to curb overcapacity will benefit prices. Futures in London advanced as much as 1.7 percent to $1,963.50 a ton, the highest price since May 26, and traded at $1,940.50.

LME nickel fell 0.7 percent after closing at the highest in three months. On Monday, Philippine President Rodrigo Duterte had threatened to impose more taxes on mining firms unless they take steps to protect the environment, reviving concerns about supply from the world’s top producer of mined nickel.